The performance improvement of electronic devices such as bipolar transistors and field-effect transistors has dramatically increased the operating speed of large-scale integrated circuits (LSI). However, despite high speed operation inside LSI, the interconnection speed at the level of the printed circuit board on which the LSI is mounted is set lower than inside LSI, and the interconnection speed at the level of the rack on which the printed circuit board is installed is set even lower. These are attributed to the increase of transmission loss, noise, and electromagnetic interference associated with the increase of operating frequency, because a longer interconnect requires a lower operating frequency in order to ensure adequate signal quality. Hence, a recent growing trend in electrically interconnected apparatuses is that mounting technology is more dominant in system performance than LSI speed.
In view of the foregoing problem with electrically interconnected apparatuses, some proposals have been made for an optically interconnected apparatus, which includes optical interconnection between LSIs (e.g., JP-A 2004-241630 (Kokai), hereinafter referred to as Patent Document 1). Optical interconnection has little frequency dependence of loss in the frequency range from DC to 100 GHz or more, and free from electromagnetic interference with the interconnect path and noise due to ground potential difference, allowing interconnection at several 10 Gbps to be easily realized. Cost-effective optical interconnection requires an optical transmission system that can ensure large mounting margin and operating margin with simple configuration. However, the conventional technique mentioned above relates to enhancing light collection performance in the light receiving section of a semiconductor light receiving device, yet inadequate for ensuring mounting margin in the external optical coupling of a semiconductor light receiving device.